Dynamics of two multi-stemmed understory shrubs in two temperate forests.

Xuejiao Bai,Tania Brenes-Arguedas,Xugao Wang,Fei Lin,Ji Ye,Zuoqiang Yuan,Shuai Shi,Zhanqing Hao,Dingliang Xing,Ben Bond-Lamberty

doi:10.1371/journal.pone.0098200

Abstract

A multi-stemmed growth form may be an important trait enabling the persistence of individual shrubs in the forest understory. With the aim of evaluating the role of multiple stems, neighbor competition and soil nutrients in shrub performance, we study the dynamics of two temperate multi-stemmed shrub species. We modeled stem growth and survival of Corylus mandshurica and Acer barbinerve in two temperate forests with differing structure in northeastern China. One forest was an old growth broad-leaved Korean pine (Pinus koraiensis) mixed forest; the other was a secondary poplar-birch forest. Growth of the two species and survival of C. mandshurica increased with stem number in the old growth forest, but not the secondary forest, suggesting the benefits of a multi-stemmed growth form are facultative. C. mandshurica also suffered more from overstory neighbor competition in the old growth forest, which may suggest that this species is less shade-tolerant than A. barbinerve. Moreover, the performance of the two species were clearly influenced by understory neighbors and soil variables in the old growth forest relative to the secondary forest, which may be due to different forest structure. We conclude that multiple stems are not always important for the persistence of shrub species. Even within the same species, the multi-stemmed benefits might be facultative, differing among forests and neighborhood compositions.

Highlights

While forest studies often focus on tree dynamics, shrubs are ubiquitous components of the forest community, and their dynamics differ from dominant trees in important ways
Study species Here we focus on the stem growth and survival dynamics of two shrub species that are most abundant in the understory of both forest types
Stems of 1 cm dbh grew on average 0.20060.005 cm2?yr21 in the old growth forest, and this increased to 0.25660.051 cm2?yr21 for stems of 3 cm dbh

Summary

Introduction

While forest studies often focus on tree dynamics, shrubs are ubiquitous components of the forest community, and their dynamics differ from dominant trees in important ways. The demographic traits of understory shrub species are fundamentally different from overstory tall tree species. The dynamics of understory shrubs are mostly driven by vegetative growth and mechanical damage to stems [6]. Unlike overstory tall trees, shrubs can spend all their life in the forest understory. In multi-stemmed shrubs, each stem may experience recruitment, growth, and death semi-independently. Such shrubs usually consist of stems of different ages and sizes [8]. Competition among stems within a shrub might restrict height growth relative to single-stemmed trees [9], while more stems can increase overall plant survival compared with individuals of the same species with fewer stems [10]

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Conclusion